It is an important problem to increase the energy density of a positive electrode when a lithium-ion secondary battery having a high energy density is developed. It is possible to increase the density of a positive electrode mixture which mainly contains a positive electrode active material, a conductive agent, and a binder, to increase the energy density of the positive electrode.
On the other hand, an excellent capacity retention is also required for the lithium-ion secondary battery. In order to achieve the excellent capacity retention, for example, the preventing the deterioration in an electrode is considered.